Association between paraoxonase 1 -108C/T polymorphism and coronary heart disease: an updated meta-analysis

Background At present, no consensus is reached among articles that investigate the relationship of paraoxonase 1(PON1) -108C/T polymorphism with susceptibility of coronary heart disease (CHD) so far. In this regard, the present meta-analysis was conducted to comprehensively review existing articles related to the relationship of PON1 -108C/T polymorphism with CHD susceptibility. It was preregistered in the International Platform of Registered Systematic Review and Meta-Analysis Protocols (INPLASY)-INPLASY202430117. Methods Articles that explored the relationship between PON1 -108C/T polymorphism and CHD incidence were searched from electronic databases according to our preset study selection criteria. Thereafter, we adopted stata 12.0 software to analyze our screened studies. At the same time, odds ratios (ORs) and related 95% confidence intervals (95% CIs) were determined for evaluating association strength. Results At last, this meta-analysis selected altogether 13 case-control studies that involved 2,979 cases and 2,887 control subjects. We found that the PON1 -108C/T polymorphism displayed marked relationship with CHD susceptibility (T vs. C: OR = 1.24, 95% CI 1.07–1.45; CT vs. CC: OR = 1.33, 95% CI 1.17–1.52; TT vs. CC: OR = 1.51, 95% CI 1.09–2.09; Recessive model: OR = 1.16, 95% CI 0.93–1.45; Dominant model: OR = 1.45, 95% CI 1.16–1.81). Moreover, subgroup analysis showed that race and sample size had no impact on the results. Bioinformatics analysis showed that -108C>T polymorphism was relation to PON1 gene expression (https://gtexportal.org/home/). Conclusions The PON1 -108T allele is identified as the possible low-penetrant risk factor of CHD, as suggested by our present meta-analysis. Systematic Review Registration: https://inplasy.com/inplasy-2024-3-0117/, Identifier INPLASY202430117.


Introduction
Coronary heart disease (CHD) represents a leading cause resulting in disability and mortality worldwide, which also becomes a main public health issue (1).Although our knowledge of CHD has advanced considerably, the detailed pathogenesis of CHD remains unclear.A series of modifiable and non-modifiable risk factors can influence the formation of atherosclerotic plaque, including age, gender, smoking habit, intake of alcohol, physical inactivity, overweight/obesity, abnormal lipid profile, high blood pressure, as well as family history of CHD (2,3).Paraoxonase (PON) family includes PON1, PON2, and PON3.PONl and PON3 belong to secretory enzymes, which are mainly expressed in liver and kidney tissues, and are closely bound to high-density lipoprotein in serum.PON2 belongs to intracellular enzymes and can be widely expressed in various tissue cells.In PON family, domestic and foreign scholars have conducted the most comprehensive and in-depth research on PON1.PON1 is the HDL-related Ca2+ dependent glycoprotein (lactonase), which presents antioxidant and anti-atherogenic features through paraoxon hydrolysis (4).
PON1 is an HDL-associated esterase that hydrolyses lipoperoxides.It acts as a protective factor against oxidative modifications of LDL, indicating that it possibly exerts an important part in preventing atherosclerotic process.This has led to the hypothesis that the lower the PON1 activity is, the higher will be the accumulation of oxidized LDL and risk of CHD.Recent meta-analysis showed that PON-1 activity is significantly lower in CAD patients.In human being, PON1 locates within q21.3-q22.1 in chromosome 7 long arm.The PON1 gene has nearly 200 single nucleotide polymorphisms (SNPs).Notably, the PON1 -108 polymorphism promoter region [c.-108C>T (C: cytosine T: thymine); dbSNP: rs705379; OMIM database: +1688200003] greatly affects PON1 function.Besides, in certain cellular systems, the -108C/T polymorphism of this gene takes up 23% expression of PON1, while -108TT constructs decreased PON1 level relative to -108CC constructs.
Many articles are conducted to analyze the association of PON1 -108C>T polymorphisms with CHD susceptibility, however, no consensus results are obtained so far.According to a previous systematic review, the PON1 -108C>T may be potential CHD risk factors.Due to three missing eligible studies, this metaanalysis did not include all potentially relevant studies.In addition, previous meta-analysis did not use subgroup analysis and bioinformatics analysis.To evaluate the impact of PON1 -108C>T polymorphism on CHD clinical outcomes, we conducted the current updated meta-analysis.

Search strategy
This meta-analysis was implemented according to PRISMA checklist (Attachment 1).With the guidance of Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines we has completed our meta-analysis protocol, and has been registered in the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY) with the number is INPLASY202430117.Web of Science, PubMed, CNKI and Embase were systemically retrieved to enroll eligible articles published before June 2020.The keywords shown below were used, including "paraoxonase 1", "paraoxonase-1", "PON 1", "PON-1", "variant", "variation", "mutation", "SNP", "polymorphism", "atherosclerosis", "arteriosclerosis", "coronary heart disease", "coronary artery disease", "acute coronary syndrome", "myocardialinfarction".Besides, reference lists were manually searched to prevent omitting any eligible study.

Inclusion and exclusion
We selected studies based on the following criteria: (a) casecontrol articles evaluating the relationship of PON1 -108C>T with CHD susceptibility; (b) studies conducted by enrolling irrelevant subjects; (c) studies with enough data on ORs and 95% CIs.At the same time, reports, reviews, letters and comments were eliminated from this study.For duplicates, the one that had the greatest sample size was adopted for the present meta-analysis.

Data extraction
Two independent investigators collected data and were also responsible for result checking.Data extracted were as follows, first author, publication year, area, case/control numbers, frequencies of genotypes among cases/controls, along with Hardy-Weinberg equilibrium (HWE) evidence among controls.Any disagreement between them was settled down by mutual negotiation.

Statistical analysis
HWE among controls of every article was assessed through chisquare test, with P < 0.05 indicating significance of disequilibrium.Besides, ORs and 95%CIs were adopted for estimating the association strength of PON1 -108C>T polymorphism with CHD risk through allele model (T vs. C), heterozygote comparison (CT vs. CC), homozygote comparison (TT vs. CC), recessive model (TT vs. CT + CC) and dominant model (TT + CT vs. CC).In addition, chi-square test was conducted to quantify the heterogeneity influence, with I 2 > 50% suggesting that there was heterogeneity among different studies, as a result, a random effects model should be selected; else, the fixed effects model should be used.We also conducted sensitivity for evaluating result stability through eliminating a study each time for determining its impact on combined ORs.Furthermore, Begg's funnel plot was employed to investigate the bias of publication, with P < 0.05 indicating the presence of significant bias of publication.STATA12.0 (Stata Corporation, College Station, Texas) was utilized for meta-analysis.

Characteristics of included studies
Figure 1 presents the study screening procedure.Altogether 526 relevant papers were identified from Web of Science, PubMed, CNKI and Embase.Finally, we enrolled 13 case-control studies into the present meta-analysis (5)(6)(7)(8)(9)(10)(11)(12)(13)(14).These studies were published between 2000 and 2020.The detailed information of the included papers was demonstrated in Table 1.Of these, four studies focused on Caucasians, nine studies focused on Asians.The genetic distributions of controls conformed to HWE among the enrolled studies, with the only exception of Ahmad et al.The general features of the eight researches were summarized in Table 2.

Meta-analysis results
Table 1 and Figure 2 display the association of PON1 -108C>T polymorphism with CHD incidence.It was observed that, PON1 -108T polymorphism showed significant correlation with CHD incidence (T vs. C: OR = 1.24, 95% CI 1.07-1.45;CT vs. CC: OR = 1.33, 95% CI 1.17-1.52;TT vs. CC: OR = 1.51, 95% CI 1.09-2.09;Recessive model: OR = 1.16, 95% CI 0.93-1.45;Dominant model: OR = 1.45, 95% CI 1.16-1.81).In addition, significant association was found from subgroup analyses based on HWE, sample size and race.Sensitivity analysis was also conducted, which suggested that none of the enrolled studies had significant influence on the combined ORs, indicating our result stability.The cumulative metaanalyses showed a increasing trend in the estimated risk effect, The flowchart of the included studies in the meta-analysis.

Sensitivity analysis
Sensitivity analysis was performed by omitting each study in turn to evaluate the influence of single studies on the overall estimation (Figure 4).The corresponding pooled OR and significant results did not change materially, indicating that our results were statistically robust.

Publication bias
We visualized the funnel plot to analyze the potential bias of publication, and no obvious bias of publication was detected (Figure 5), which indicated that the present meta-analysis had low bias of publication.

Functional predictions
The GTEx portal shows a significant correlation between PON1 -108C>T polymorphism and heart PON1 gene expression.In detail, the T allele of PON1 -108C>T polymorphism significantly correlated with decreased PON1 expression (Figure 6).

Discussion
CHD represents a disorder that involves multiple factors, and its etiology remains largely unclear at present.It has been increasingly suggested that CHD results from the complicated interactions among genetic and environmental factors.PON1, an enzyme related to HDL-C, can resist the peroxidation of LDL-C.The decreased PON1 activity has been suggested to induce an increased incidence of coronary atherosclerosis (12).Besides, -108TT has been previously reported to down-regulate the PON1 level relative to the -108CC constructs (7).In this regard, we predicted that PON1 -108T might participate in CHD incidence.PON1 -108C>T polymorphism is previously suggested to be   Forest plot for meta-analysis of the association between the PON1 -108C/T and CHD risk.Cumulative meta-analysis for PON1 -108C/T polymorphism and CHD.This meta-analysis enrolled 13 case-control studies that involved 2,979 patients along with 2,887 controls, which aimed to examine the association between PON1 -108C>T polymorphism and CHD susceptibility.As far as we know, the Sensitivity analysis of the association between the PON1 -108C/T and CHD risk.present meta-analysis was the first to comprehensively assess the correlation between PON1 -108C>T polymorphism and CHD susceptibility.Overall, PON1 -108C>T polymorphism was significantly associated with CHD incidence among all the studied populations.Due to different living environments and genetic backgrounds, subgroup analysis based on race was also conducted, which indicated that PON1 -108C>T polymorphism showed obvious relation with CHD susceptibility among the Asian and Caucasian populations.After that, subgroup analysis based on sample size showed that the sample size had no impact on the results.Furthermore, we also conducted sensitivity analysis, which revealed that this polymorphism was markedly correlated with CHD susceptibility.There was no obvious evidence regarding the bias of publication detected.Due to the limited sample size, our results must be further investigated.This study did not illustrate the related mechanism of such relation.Previous study and our bioinformatics analysis found that -108T allele decreased PON1 level (8).PON1 is believed to promote the anti-inflammatory and anti-oxidant functions of lipoproteins (11).Ultimately, decreased PON1 led to the occurrence and progression of CHD.Moreover, Bouman et al. demonstrated that PON1 is the rate-limiting enzyme in the second step of clopidogrel bioactivation, in which 2-oxo-clopidogrel is hydrolyzed into the active thiol molecule.An analysis of 112 individuals revealed that the PON1 -108C>T polymorphism is the major factor affecting clopidogrel bioactivation (14).
Certain limitations must be noted in this meta-analysis.Firstly, this meta-analysis was carried out according to the non-adjusted ORs, since ORs were not available in each study and the available ORs were unadjusted relative to identical possible confounding factors, like exposure, age and sex.The insufficient information for data analysis possibly induced severe confounding bias.Secondly, the insufficient raw materials prevented us from better evaluating the possible associations between genes and the environment or between genes.Thirdly, only few studies and participants were involved in certain subgroups-based meta-analysis.

Conclusions
To sum up, this meta-analysis indicates the relationship of PON1 -108C>T polymorphism with CHD susceptibility.More articles that estimate the impacts of interactions between genes and between genes and the environment are needed to further and comprehensively understand the correlation between PON1 -108C>T polymorphism and CHD susceptibility.

FIGURE 3
FIGURE 3 related to CHD incidence, yet no consistent findings are obtained.For clarifying those heterogeneous results, the present metaanalysis was conducted aiming to examine the association between PON1 -108C>T polymorphism and CHD susceptibility.

TABLE 1 Summary
ORs and 95% CI of PON1 -108C>T polymorphism with CHD risk.
a Number of comparisons.

TABLE 2
Included studies of the PON1 -108C>T polymorphism with CHD.